Fluid propeller



June 12, 1945. i w UPSQN v 2378,049

FLUID PROPELLER Filed Nov. 29, 1941 I'INVENTO-R. WALTER L; UPSON Patented June 12, 1945 UNITED STATES PATENT OFFICE 2,378,049 T FLUID I'ROPELLER WalterL. Upson, Litchfield, Conn assignor to The Torrington Manufacturing. 00., Torrington, Conn., a corporation of Connecticut Application November 29, 1941, Serial No. 420,970

1 Claim.

This invention relates to improvements in fluid propellers, and more particularly to a propellertype fluidreaction device such as a fan of a, design adapted for operation with improved efficiency for both free air and certain pressure uses. Certain principles and features of the present improvements are susceptible of embodiment in fluid reaction devices generally.

The invention is herein described, for brevity and exemplary illustration, in reference to a propeller type fan which is adapted for quiet operation with improved efficiency for fluid-moving purposes generally, and which is susceptible of more than the usual variety of applications in service. Such applications include installations wherein the fan is required to deliver a fluid, uch as air, under a light or moderate pressure head as in certain duct installations, and is equally adapted for use in all free-air units such as desk fans, room air circulators and the like. The attainment of the foregoing advantages constitute a broad statement of the principal objects of the invention.

Somewhat more particularly expressed, the invention objectively results in a propeller type fan capable of use either for free air purposes or as a pressure fan of a type such as to minimize losses through shunting or recirculation of air through the central area of the fan, as has heretofore been experienced in certain types of propellers-of relatively open center construction.

Yet another object of the invention is attained in a, fan of improved design in which both the disc area and the diameter are minimized in comparison with the more usual and prevalent types of propellers of comparable delivery characteristics.

A further object of the invention is attained in a novel disposition and design of substantially the major active portion of each of the blades of a multiple blade propeller fan, from which there is virtually attained an equivalent of so-called wide blade fans of some greater diameter than those of the present designs having comparable airdelivery characteristics.

An additional objective of present design is realized in an arrangement of the blades of a multi-blade propeller fan, substantially, although not necessarily entirely, at one side or'rearwardly of a. center disc through which, as with a hub, the propeller is mounted for rotation.

A further object of the invention, considered from a structural point of view, is realized in a fan which may be of one-piece construction and which exhibits an improved degree'of stiffness and resistance to deflection or deformation of blades, than is .the case with one-piece propeller fans of the more usual and prevalent types.

An important object of the present improvements is attained in a greater axial space economy in an assembly of fan and driving motor therefor, either alone, or when installed adjacent to a grille or the like, or when mounted interiorly of an air duct or conduit; in the examples disclosed, this advantage is attained in a propeller which is markedly centrally hollowed or cupped in aspect, in such manner that the planes'transverse of the axis of rotation in which the major reaction surfaces operate, may extend through at least a part of a driving motor for the fan so as to enable a substantially foreshortened assembly of fan and motor, resulting in a reduced overall axial dimension of the assembly.

In reference to preferred practice in forming the propeller, a, further object of the invention is attained in a propeller design which may be formed With'a relatively low wastage of material from sheet metal stock, in such manner that, except for certain portions adjacent the peripheral parts of the blades, a single disc of the metal may be utilized without any substantial wastage of stock; the design further results in an angularly extensive zone of anchorage of each of the blades with a central disc or spider portion, making for an unusually rigid one-piece propeller.

The foregoing and numerous objects and advantages will more clearly appear from the following detailed description of certain preferred embodiments of the invention, as applied to propeller type fans, particularly when considered in connection with the accompanying drawing, in

which: 7

Fig, 1 is a front elevation of a propeller type fan embodying the present improvements; Fig. 2 is a side or edge elevational view of th fan shown by Fig. 1; Fig. 3 is a transverse sectional elevation taken in staggered planes parallel to and including the axis of revolution of the fan of Fig. 1, and further showing a suggested arrangement of mounting the fan and motor assemblywithin a duct or shroud ring about the fan, and adjacent a grille across the terminus of the duct; Fig. 4 is a transverse section through one of the blades of the fan of Fig. 1 as indicated along line 4-4 thereof Fig. 5 is a sectional view through one of the blades of the fan of Fig. 1, as taken along staggered planes as indicated by line 55 of Fig. 4;

Fig. 6 is a plan view of a blank suitable for forming a fan similar to that shown by Fig. 1, the blank being illustrated as it would appear prior to final blade formation, and Fig. 7 is a front elevationof a slightly modified form of propeller, which may also be formed from the blank shown by Fig 6 Referring by characters of reference to the drawing, it will appear that each of the illustrated embodiments of the improvements is formed up as a one-piece fan, i. e., one in which a center disc or spider portion and the blades proper are formed of a single blank or stamping, as of sheet metal. It will be understood of course that the invention is by no means restricted in its scope to fans of so-called one-piece type, nor is it restricted in a, broad sense to fans in which the blade elements or center disc or both, are formed of sheet metal or other specific material; obviously the structure may be embodied, forexample, in a fan of molded plastic or of rubber construction. For simplicity and brevity of description, however, the illustrativ embodiments are described in reference to one-piece sheet metal fans.

Not only the manner of blanking or stamping the disc, prior to forming up by imparting the pitch and other curve characteristics to the blades, but the structural features of the fan will probably be best understood by first referringto Fig. 6'. This figure of drawing illustrates a fiat planar blank, struck out by cutting dies or by shearing, say from a sheet of aluminum or steel. The blank indicated at 10, is characterized by a defined, preferably but not necessarily, circular center-disc-forming portion ll, projecting outwardly of which are the several blade-forming bodies l2 which, when formed up, result in the individual blades of the fan.

The number of blades is optional within reasonable limits, but for most types of service, in fans say of 6" to diameters, a fiveor six-blade fan has been found to give a somewhat better structure and performance than those of a greater or lesser number of blades.

The blank I0 is characterized, as will appear from Fig. 6, by a plurality of channels or slots I3. Each of these slots, in a five blade fan, may be rectilinear and approach tangency to a circle only slightly less in diameter than the outer circle defining the periphery of the center-disc-forming portion H. An equally preferred arrangement consists in slightly curving these slots or channels, in which case a straight line connecting their ends will approximate a tangent relation to a circle of nearly the diameter of the periphery of portion II. If desired, and as shown, the inner ends of the channels or slots may be somewhat rounded as shown at M, which inner end portions, in a five blade fan will preferably lie at a 72 angular spacing about the perimeter of the center disc-forming-portion ll.

It will appear obvious from observation of the fan blank of Fig. 6 that, upon curving and shaping the blades I2, the channels l3 will result in adjacent metal margins defining respectively a trailing edge and a leading edge of the adjacent blades, as will later better appear.

Observing now the peripheral formation of the blank, it will appear that in the blanking step, in a five blade fan, five V-like reentrant portions are removed as indicated at 15, these portions being somewhat more widely curved on one side than on the other, but each being curved on a radius substantially within the confines of the blade thus outlined. The locations of centers of these two curved outer margins of each blade, are indicated respectively at 6 for the wider curve, and at I! for the curve on the smaller radius. As

will later appear, although there is some preference for locating the wider curve along the leading margin of the blade, the leading and trailing margins may be reversed, according to the direction given the blades in respect to the center disc at the time of forming upafter blanking, as will later better appear. It is obvious that the original blade blank, being in planar form, will possess a somewhat greater diameter than that of the fan after forming. This is particularly true in a fan of the present design because of the relatively sharp backsweep of the blades hereinafter described. 0

Observation of the blank shown by Fig. 6 will further indicate to those experienced in the art of propeller fan manufacture, that the arrangement illustrated and just described, results in a relatively low percentage of waste material in blanking out the fan from a circular sheet of material. It will further appear that, due to the initial adjacence of the metal portions forming leading and trailing margins of adjacent blades, there results practically no waste of metal at all, say in the intermediate three-quarters of total blank area. A further important advantage results from the fact of carrying the blade-forming margins in close adjacence to each other fully inwardly to the periphery of the center discforming portion ll. From this it results that the supporting margin of each of the blades proper is of the greatest possible angular extent, resulting in greater rigidity of the fan, since each of the blades is anchored or supported, in a five blade fan, over substantially a full one-fifth of the periphery of the center disc. The same relation would prevail say in a six blade fan, wherein the angle of support on the center disc would be close to 60, or one-sixth of the full circle of the center disc. It is obvious of course that some relatively minor diminution of aliquot parts of the full circle of support, would fall within the scope and intendment of the present design and the claims thereto.

Proceeding now to a description of the method of forming up the propeller from the blank 10 as shown by Fig. 6, although there is no invariable sequence of imparting the difierent curvatures of the several blade portions, it will usually be preferred first to impart a distinct back-sweep to the innermost portion of each of the blades. By this is meant a folding or bending of a. quasitriangular portion away from the curved margin of the center disc, so that such portion extends rearwardly of the plane of the center disc 20 in the leading portion of the inner end of the blade, say at an angle of the order of Substantially this same angle of rearward bend prevails over the greater part of the width of the supported end of each blade. The quasi-triangular portion gradually tapers in width to a zone on the inner trailing margin of the blade where its width and backsweep become virtually zero. The leading margin, thus having the greatest angularity with a plane transverse to the axis of revolution of the fan, is indicated at 2! and the trailing margin of such area at 22. The resulting quasi-triangular portion 23 is thus shown as bounded, as to two legs, by curved lines, the inner of which is the described are of the outer circle of the center disc '20. and the outer of which is an arcuate zone 24 drawn on a radius which is within but close to the periphery of the center disc. The thusformed quasi-triangular or three-sided area 23 of eachblade, because of its very sharp rearward projection, stepped aspect, or sweepback trend, results in a secondary arm, since the shaping of zone 24 serves in large measure to impart'the desired pitch to the remainder of the blade. Since the area 23does notlie parallel tothe axis of revolution, and exhibits a substantial area which is protuberant, convex as shown, when viewed toward the delivery face of the blade, it partakes appreciably of the nature of a propellentype reaction surface. In operation of the fan, the air attacked by portion 23 is in part impelled outwardly to eifect a gradual engagement thereof by the'outer major area of the blade which is concave-convex in form, and is indicated at 25.

Considering further each of the blade elements of the fan, as a unit, it will be seen that the major propeller reaction surface generally identified by the numeral25, extends from the arcuate zone 24, defining a relatively gradual break or merging channel at this point, whence the blade, although preferably concavo-convex, is nearly flat as will probably best appear from the section of Fig. 3. By preference, the angularity in the leading portions of the blade, between parts 23 and. 25 is of the order of l35150.

As will best appear from one of the plan views, say Fig. 1, each of the blades is so outlined after forming up, as to present about equal areas on opposite sides of a preferably uniformly curved median line indicated at 26, from the trend of. which it will be seen that each of the blades, as viewed in plan, has a very marked comets tail trend resulting in what may be termed a pin-wheel aspect of the fan in front elevation. Although shown in Fig. 1 in an arrangement such that each of the blades is of a backward trend when viewed in reference to the direction of rotation, as indicated by the arrow, the same blank a shown by Fig. 6, may be formed, by bending the blades similarly but by folding them to the opposite sides of the plane of the center disc, in such'manner that the sweep of each blade, in plan, and hence the trend of its median 26. is in a direction forward rather than backward; it is accordingly to be understood that the trend of blade median herein referred to, is not restrictive of direction, but is used for brevity in denoting'a sharply sweeping curvature of each blade, in either direction in reference to rotation. It will be noted that both of the embodiments shown by Figs. 1 and 7, are made up for similar rotation, being clockwise or right-hand propellers.-

Referring now to that margin which in Fig. l is shown as a leadingmargin of each blade, and indicated at 30, such margin is or may be formed along a smooth curve which is regular (or only slightly irregular) on a radius or radii within the inner trailing portion of the blade. The formation of blade and margin 30, are such that this edge constitutes a continuous lateral and peripheral boundary. In the arrangement of Fig. 1, a smoothly curved margin 30 terminates in a rounded corner portion 3| formed on a relatively short radius as will appear from Fig. 6, whence the edge of the blade continues reentrantly of the blade area,- in a substantially rectilinear tangential margin 32. In a fan formed as shown by Fig. 1, margin 32 constitutes the trailing edge.

As thus far described in relation to a somewhat preferred embodiment shown by, Figs. 1 through 5, the fan blade elements have been represented as folded or bent out of the blank I in such manner that the relatively widely curved margin 30 constitutesthe leading edge of the reaction element 25 of the blade, and the relatively straight line margin 32 thereof, constitutes its trailing margin. It will. however be observed that the blank ID of Fig. 6 lends itself equally to a blade formation resulting from folding or bending the blade elements in a relatively opposite direction fromthe center disc of the blank, thus resulting in a relatively reverse relation of the rectilinear and curved margins. A fan resulting'from this relatively opposite formation of the blade is shown by Fig. 7. Since, but for the opposite relation of blades, the curvatures of their various portions remain substantially as heretofore described, it is felt 'suflicient 'to note that in the modified arrangement, a center disc 40, shown as circularly bounded by line 4|, primarily supports a series of somewhat triangular, convex elements 42, each outwardly bounded by an arcuate' channel 43. The blade is continued from channel 43 outwardly to constitute the major propeller reaction surface 44, which is preferably curved in forming to impart thereto a concavo-convex shape. It is noted that the portion 42 corresponds generallyto the element 23 of the form first described, and the-portion 44 corresponds to'that initially indicated at 25. In the modification however, the leading margin of each blade indicated at 45 is shaped approximately like the margin 32 of Fig. l, and, the broad, substantially regularly curved margin 46 corresponds generally to the margin 30, except that edge 46 now becomes the trailing margin of the; blade. The 'modified arrangement is better suited for certain types of service.

An examination and comparison of the several sections of the blades as shown by Figs. 3, 4 and 5 and the side or edge view of the fan as shown by Fig. 2, will serve to indicate the degree of pitch preferably employed in fans of the. more prevalent diameters. It will be noted however that the blade curvature or camber of the major propeller reaction portions 25 or 44, is by preference only slight. It may be noted as a preference to provide an appreciable, yet very shallow channel in each of the blades, somewhat-as indicated by numeral 50 in Fig. l, and 52 in the modification of Fig-'7 in which" the curvature of the channel 52 may be'identical with the curvature of the channel 50 in Figs. 1, l-and other showings. This channel is adjacent to, and bounds the portions, 25 or 44; it opens freely outward at the blade periphery, and is preferably tangent. if produced, to a substantial circle drawn on the axis of blade revolution as a center.

' It will be noted particularly from the side View of Fig; 2 and the partially sectional elevation of Fig. 3, that the present design varies the moreprevalent practice of disposing. the blades each partly on opposite sides of the plane of the center disc or spider portion. The present preference is to locate the blades substantially, but not necessarily fully entirely, at one or the rear side of the plane of the center disc. tively imperforate center disc and the close adjacence of the inner or supporting ends'of the blades, it will be obvious that there is but a minimum opportunity, when the fan is employed against moderate pressure heads, for the'fiuid to be recirculated orshunted back through the center disc area of the fan as often occurs with the more open. center constructions of prevailing type propellers.

types is also minimized, in fact substantially ob viated by the wide and broadly backswept portions of the blades such as 23 or 42, Which tend to deflect the fluid somewhat outwardly from the relatively slower moving center part of the fan.

It will also appear from the widened attack- Due to the rela- This tendency of former' ins end of each of theelements 23 that there results 'a substantially wide airreceivin throat between the inner adjacent margins of the adjacent blades, which enhances the air pickup properties of this portion of the structure when in revolution, in such manner that the fan in operation does not exhibit the more usual turbulence and recirculation effects, but serves to impel in virtually straight lines away from the fan, a substantially solid and defined stream of fluid. The fans of the designs described are extreme ly quiet in operation and highly efiicient as indicated by extended tests and usage under a variety of conditions. This is true whether the improved propellers be embodied in free-air or pressuretype units, as when employed in window ventilating units or in duct systems against moderate pressures.

- Asexem olifying an advantageous structural feature of the present design, there is shown by Fig. 3 an assembly of one of the present fans provided with a driving motor 60 mounted on a suitable support 61 within a shroud ring or duct 82, and adjacent a terminus of such duct, for example, an outlet thereof. Across the outlet is mounted a grille 53. It will at once appear from the fact of mounting the blades 2325 substantially at the rear of the plane of the center disc 20, that the margins, say the trailing margins 32 of the blades, may be brought into close adjacence to the grille 63, in fact'requiring only an operative clearance therewith. This facility and advantage will appear from Figs. 2 and 3, wherein it is seen that, in this form, the trailing margins 32 of the several blades, liesubstantially in the plane of the center disc 20. This is of a marked advantage in delivering an increased proportion of the air through the grille without recirculation thereof into the fan, and further results, as will appear obvious, in a marked axial space economy of the assembly. It will further appear that the sharp sweepback imparted to the portions 23 results in what may be termed a cupped formation of the fan resulting in a substantially hollow aspect of the rear surface of the fan in such manner that the major reaction portions of the blades will overlie, and the cupped portion serve to receive a substantial part of the frame of the motor 59, thus further economizing'in overall axial space requirements.

It will be noted for completeness, that at the time of punching or shearing the blank, or thereaftenthere may be provided, as by punching or drilling, a center aperture 64 which serves to receive a hub 55, the latter being secured to the center disc 20 as by spunover or upset portions 66. A usual set screw 61 conveniently secures the hub 65 and hence the fan. to the motor shaft 68.

A marked production advantage inherent in the described manner of formation,particularly of the blanks I3. lies in the fact that irrespective of the nature of service for which the fan is desired, i. e. whether free-air or pressure fans, a

scription of features of the structure, the substantial depth resulting from the cupped or hollowed aspeot'of the. propeller, provides a fan structure which is characterized by considerably greater delivery capacity in proportion to its diameter, than is the case with the prevalent older types of propellers of the same diameter and disc. area. It may be noted that while there is some variation in proportion of depth of fan. to its diameter in the different fan sizes, most of the units constructed in accordance with the designs described will exhibit an overall depth or axial dimension of the order of one-fourth of their respective diameters. Since the greater part of the elfect is attained from the more rapidly moving outer portions of the fan and the wider blade portions near the periphery, it will appear that the embodiments of the present features result in a relatively high ratio of CFM to diameter, thus adapting the fan admirably'to conditions wherein fan disc areas must be minimized. 1

Although the invention has been described by making a fully detailed reference to certain pres-- ently preferred embodiments, such detail of description is to be understood in an instructive rather than a limitin sense, many changes being possible within the scope of the claim hereunto appended.

I claim as my invention:

A one-piece propeller type fan, including a sub stantially planar center disc and a hub for shaft mounting, a plurality of blades carried by and formed integrally with the center disc, each blade being bounded by a widely and smoothly curved margin extending without abrupt change in curvature from the center disc and across one side and the periphery of the blade, at second side margin extended from the periphery reentrantly of the blade area and inwardly to the center disc; each blade being further characterized by a major concavo-convex portion, a, supplemental three-sided displacement area in the radially innermost blade portion, one side of which supplemental area is substantially the line of juncture of the blade and center disc, a second side of which is coincident with an inner part of one side margin of the blade and a third side of which is a curve on a substantial radius extending from a zone close to the periphery of the center disc and the disc terminus of one blade margin, thence extending substantially across the blade to the opposite blade margin in a zone substantially outwardly of the disc terminus of the latter blade margin, said three-sided area bein pitched to impart thereto a marked angularity relatively to the aforesaid major concavo-convex portion of the blade, and having a surface which is convex as viewed on the delivery side of the blade, and being so shaped as to impart a distinct pitch to the said major concavo-convex portion. and to dispose the entire blade wholl axially be yond the plane of the center disc, each blade being further formed to provide, within its said major concave-convex portion, and just inwardly of and along said reentrant marginal portion, a shallow rectilinear channel tangent to a circle of substantial diameter on the fan axis as a center. said channel extending from said three-sided area fully outwardly to the periphery of the blade;

, WALTER L. UPSON; 

